It is quite a lot of information, but after a while you will start to recognize things .

Note that some shown components are optional, e.g. 8098 "additional heating" --> i think it is not on all models.

Thank you for your effort! I think it's a little to complicated for me this kind of info, and beside this, electrical circuit was checked in 2 places. Monday I will go again with the car at service for even more investigations...I will come back with updates.... meanwhile, any sugestion is welcome!

My thinking is this, although I'm no mechanic.
The ECU needs to read the information from the crank and cam sensor before injecting fuel I believe, and white smoke on starting could be unburned fuel.
It seems the fuel system is fine, the sensors are fine, the injectors are fine - so it must be the glow plugs or the relay....???

I know you have tested them but do they work in the morning? Is there a way to test them heating up when you turn the ignition on?

That's a semi-mux (early 406 facelift) diagram, looks like it's Bosch with the lift pump. The later diagrams on sedre are block diagrams - click on a component to see its individual wiring. Obviously I can't post all of them and expect it to make sense...

I think this problem is looking like something is not telling the ecu the truth and, without some decent diagnoses, finding it is just going to be changing components until the fault clears (standard practice for most franchises these days)

I would disconnect the output wire (1183) from the glow plug relay & connect it direct to the battery +ve
Measure the current if you can, (something like 30 - 40 A.), if you can't at least confirm there's a nice fat spark
If not, re-check all the connections to the glow plugs and verify the engine earth is OK

Once you're certain they're working keep the power on them for 20 seconds, start engine, keep them on for another half minute......

I would disconnect the output wire (1183) from the glow plug relay & connect it direct to the battery +ve
Measure the current if you can, (something like 30 - 40 A.), if you can't at least confirm there's a nice fat spark
If not, re-check all the connections to the glow plugs and verify the engine earth is OK

Once you're certain they're working keep the power on them for 20 seconds, start engine, keep them on for another half minute......

Hi everyone,

Just an short update, if anyone is interested. The electric circuit was checked by 3 different persons, and it seems that is all good. Last week a different ECU was checked ( with all including reprograming and syncronizing) and still the same struggle on starting, so this week, cylinder head will be removed the see if the head gasket it's broken or any other parts are broken inside the engine... it's my last try....

Meanwhile, if any on you have any sugestions, please write them
Regards

I apologise if this has already been mentioned but I couldn't see it. On the back of the HP pump is a pressure regulator which also contains a very fine strainer which can become clogged and gives rise to all sorts of problems including poor starting, I had no end of trouble with the one on my C5, same engine. If you are getting white smoke from the exhaust when trying to start, ignore this.

I apologise if this has already been mentioned but I couldn't see it. On the back of the HP pump is a pressure regulator which also contains a very fine strainer which can become clogged and gives rise to all sorts of problems including poor starting, I had no end of trouble with the one on my C5, same engine. If you are getting white smoke from the exhaust when trying to start, ignore this.

Peter

Hi, Peter

Thanks for your suggestion, but a different HP pump was placed on the car ( includig a different pressure regulator) and the same poor starting, including a lot of white/slightly grey smoke, all these until the engine temperature starts rising. After this, it runs perfectly, and it blows only a little trace of smoke wich I guess it's normally, giving the fact that it's a diesel from 2002 and it has hole in the muffler

Could well be the problem. Did we determine if your car has a Bosch or Siemens fuel system?

It has a Siemens fuel system. I've changed HP pump including it's pressure regulator, 3 injectors, glow plugs, glow plugs rely, coolant temp sensor, ECU.... and none of these bring any improvements. Even now when on the day are 20+ and on the night 10+ celsius degrees, it still needs 3-4 engine spins to turn on...

Next week, a proper mechanic, not me , will connect an hose to directly from HP pump to a bottle with diesel, and also the flow back to the same bottle... I guess it's the cheapest way to check if it's a "fake air" in the engine, problem. I hope I explained it properly depite my bad english.

You could well have a tiny leak at the fuel filter, (can be too small for fuel to leak out, but air still gets in).
It's also worth checking the strainer, (filter), in the fuel tank is not blocked, this can give similar problems.

You could well have a tiny leak at the fuel filter, (can be too small for fuel to leak out, but air still gets in).
It's also worth checking the strainer, (filter), in the fuel tank is not blocked, this can give similar problems.

Hi, Doggy

Thanks for the informations. I will come back next week with news, after replacing the whole tank circuit with a bottle with diesel.